The subject matter disclosed herein relates to vortex chambers for providing tip clearance flow control.
Generally, a turbine stage of a gas engine turbine includes a row of stationary vanes followed by a row of rotating blades in an annular turbine casing. The flow of fluid through the turbine casing is partially expanded in the vanes and directed toward the rotating blades, where it is further expanded to generate required power output. For the safe mechanical operation of the turbine, there exists a minimum physical clearance requirement between the tip of the rotating blade and an interior surface of the turbine casing. Typically, turbine buckets are provided with a cover for better aerodynamic and mechanical performance. A rail protruding out of the cover is used to minimize the physical clearance between the casing and the rotating blade. This clearance requirement varies based on the rotor dynamic and thermal behaviors of the rotor and the turbine casing.
Where the clearance requirement is relatively high, high energy fluid flow escapes between the tip of the blade and the interior surface of the turbine casing without generating any useful power during turbine operations. The escaping fluid flow constitutes tip clearance loss and is one of the major sources of losses in the turbine stages. For example, in some cases, the tip clearance losses constitute 20-25% of the total losses in a turbine stage.
Any reduction in the amount of tip clearance flow can result in a direct gain in power and performance of the turbine stage. Typically, such reductions can be achieved by reducing the physical clearance between the rotor tip and the casing. This reduction, however, also increases the chance of damaging rubbing between the rotating and stationary components.
In addition, turbine engine performance may depend on an amount of cooling and sealing air used to protect the turbine components from high temperatures that exist in hot gas paths. The cooling flow is generally used in the cooling of components and in the purging of cavities that are open to the hot gaspaths. That is, hot gas ingestion to, for example, a wheelspace may be prevented by providing a positive outward flow of cooling air through gaps. Generally, these cooling flows are extracted from the compressor portion of the engine, where any extraction is a penalty to the overall performance of the engine.